Remarks on the Origin of the Contemporary Modal Logic

Abstract

In the article a justification is presented of introducing the logics of strict implication that can be reconstructed from the works of Clarence Irving Lewis who created them. It turns out that besides the commonly mentioned arguments concerning inadequacy of the implication of the classical logic for expressing the relation of implication Lewis also gave two other motivations. Namely, he claimed that classical logic is not able to formulate the intensional meaning that he ascribed to some alternative statements of current language and that classical logic involves ontological determinism. An analysis of these arguments also supported the conclusion concerning a metalinguistic character of functors of logics of strict implication drawn on the basis of the way Lewis understood expressions of formal logic. Hence the need was emphasised of caution in applying the discussed systems for formalising philosophical reasoning. Attention was also paid to the fact that only systems S I -S3 are entirely originated by C. I. Lewis, and Oscar Becker made a major contribution towards logics S4-S5. Different origins of these systems seem to be a certain explanation for their semantic heterogeneity.